The Effect of Zinc Supplementation on Biomarkers of Zinc, Iron, and Copper Status in School Children in Guatemala Pubblico
Bui, Vinh Quang (2011)
Abstract
The Effect of Zinc Supplementation on Biomarkers of Zinc, Iron, and Copper Status in School Children in Guatemala
by
Vinh Quang Bui
Preventive zinc supplementation is beneficial for children with
high risk of zinc deficiency, but its adverse effect on biomarkers
of iron and copper status is still a great concern.
A randomized controlled trial of zinc supplementation was conducted in five public schools in a low-income urban area in Guatemala City from January to October 2006. Eligible children aged 6-11 years were randomly allocated to receive daily chewable tablets of 10 mg zinc oxide or placebo for six months. All the children concurrently received fortified milk (daily 200 ml of whole milk, containing 1.6 mg zinc and 1.1 mg iron). Participants (n= 720) had high risk of zinc deficiency (21.6% low serum zinc and 39.4% low dietary zinc intakes). At baseline, serum ferritin and copper concentrations correlated with serum C-reactive protein concentration (p <0.001), but serum zinc and zinc-related biomarkers did not (p >0.05). Serum ferritin and copper concentrations were associated with high CRP levels, starting from the CRP >0.5 mg/L level (p<0.001). Among zinc biomarkers (i.e., serum zinc, ALP, and albumin), only serum zinc concentration was associated with dietary zinc intakes both before and after 6-month interventions (p ≤0.06). All significant associations and agreements were weak (r ≤0.21, kappa ≤0.12). At six-month follow-up, compared to placebo, zinc supplementation induced higher serum zinc concentration and ALP activity (p ≤0.03), but had no effect on iron or copper biomarkers (p >0.05). In the placebo group, fortified milk program improved serum zinc concentration and ALP activity (p <0.0001), but decreased serum ferritin and copper concentrations (p<0.0001).
Overall, serum CRP was associated with serum ferritin and copper, but not with serum zinc. Serum zinc concentration was consistently associated with dietary zinc intakes. Daily zinc supplementation increased zinc status but did not induce changes in iron and copper status. The fortified milk improved zinc biomarkers but decreased iron and copper biomarkers. This is the first study that observed a positive association between serum CRP and copper concentrations. The study confirms the beneficial impact of zinc supplementation on zinc status and its safety on iron and copper status.
Table of Contents
TABLES OF CONTENTS
ACKNOWLEDGEMENTS...i
TABLE OF CONTENTS...iii
LIST OF ABBREVIATIONS AND ACRONYMS...v
LIST OF TABLES...vi
LIST OF FIGURES...vii
CHAPTER 1: INTRODUCTION...1
CHAPTER 2: LITERATURE REVIEW...6
2.1. Overview of Zinc Nutrition...6
2.2. Measurements of Zinc, Iron, and Copper Status...24
2.3. Measurement Errors of Nutrition-Related Variables...44
2.4. The Effect of Inflammation on Nutrition-Related
Biomarkers...53
2.5. Pairwise Interactions among Zinc, Iron, and Copper...68
2.6. The Effect of Zinc Supplementation on Biomarkers...75
2.7. Health and Nutritional Status of Children in
Guatemala...82
CHAPTER 3: METHODS...89
3.1. Research Objectives...89
3.2. Study Design...89
3.3. Study Setting and Participants...90
3.4. Randomization and Blinding...91
3.5. Interventions...92
3.6. Unanticipated and Concurring Intervention...92
3.7. Data Collection Procedures and Study Variables...93
3.8. Definition of Variables...97
3.9. Sample Size...98
3.10. Statistical Methods...100
CHAPTER 4: MEASUREMENTS OF SERUM FERRITIN AND COPPER, BUT NOT ZINC, ARE INFLUENCED BY C-REACTIVE PROTEIN LEVELS IN GUATEMALAN SCHOOL CHILDREN...107
Abstract...110
Introduction...112
Methods...113
Results...117
Discussion...119
Cited References...124
Tables and Figures...127
CHAPTER 5: DIETARY ZINC INTAKE IS CONSISTENTLY ASSOCIATED WITH SERUM ZINC CONCENTRATION IN CROSS-SECTIONAL ANALYSES IN HEALTHY GUATEMALAN SCHOOL CHILDREN...133
Abstract...136
Introduction...137
Methods...138
Results...142
Discussion...143
Cited References...148
Tables and Figures...151
CHAPTER 6: THE EFFECT OF ZINC SUPPLEMENTATION ON BIOMARKERS OF ZINC, IRON, AND COPPER STATUS IN SCHOOL CHILDREN: A RANDOMIZED CONTROLLED TRIAL IN GUATEMALA...156
Abstract...159
Introduction...160
Methods...161
Results...167
Discussion...169
Cited References...176
Tables and Figures...179
CHAPTER 7: SUMMARY AND CONCLUSION...185
7.1. Keys Findings and Potential
Significance....186
7.2. Strengths and Limitations of the Current Study...191
7.3. Future studies...194
7.4. Implications of the Study Findings...195
7.5. Conclusion...195
LITERATURE CITED (CHAPTER I-III, AND VII)...197
APPENDICES...217
Appendix 1: Form for Summary of Admission and
Group Assignment...217
Appendix 2: Form for Socio-Economic Information...218
Appendix 3: Form for Food Frequency Questionnaire...220
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